Food or beverage container or container panel

ABSTRACT

Disclosed is a food or beverage container or container panel comprised of an aluminum alloy body having an integral bottom and wall. An intermediate layer comprised of an aluminum oxide or aluminum hydroxide layer is bonded to the aluminum alloy body and a functionalized layer of an organo phosphonate, organo phosphinate or phosphate ester is bonded to the oxide or hydroxide layer. A polymer layer is bonded to the functionalized layer. The functionalized layer is comprised of the reaction product of phosphonic or phosphinic acid and/or phosphonic acid ester, for example.

This application is a division of application Ser. No. 07/456,486, filedDec. 26, 1989, now U.S. Pat. No. 5,103,550.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a new food or beverage container or acontainer panel and a method for forming the same. More particularly,this invention relates to aluminum food or beverage containers havingcoatings of aluminum oxide or aluminum hydroxide on the metal surfaceand a layer of phosphonic/phosphinic or phosphoric acid ester materialbonded to the oxide and/or hydroxide layer.

2. Description of the Related Art

It is well known that the natural oxide on aluminum can be reinforced oraltered by several treatment methods to give better protection againstcorrosion or serve as a substrate for adhesive bonding. Such treatmentsinclude anodic oxidation, hydrothermal treatment in water, water vaporor aqueous solutions, or reaction treatments such as conversion coatingswhich employ solutions which may contain chromic acid, chromates,phosphoric acid, phosphates and fluorides.

While anodic oxides can be grown to thicknesses of tens of microns,their application is generally time consuming and requires expensiveelectrical equipment. Hydrothermal coatings are easier and faster toapply and require only simple equipment. They consist mostly of AlOOH orAl(OH)₃ in crystalline or amorphous (gelatinous) form and are generallyknown as boehmite coatings as disclosed in Wernick et al, "The SurfaceTreatment and Finishing of Aluminum and Its Alloys", ASM Publ., 1987.These coatings offer reasonably good protection in mildly aggressiveenvironments. Chemical conversion coatings, e.g., chromate-phosphatecoatings as disclosed in Wernick et al, can be applied in severalseconds to a few minutes. They afford good corrosion protection and aregood bonding substrates for polymer coatings, laminates or adhesivesalthough they do not match the adhesion and durability performance ofanodic oxides applied in phosphoric acid according to U.S. Pat. No.4,085,012.

Venables et al, U.S. Pat. No. 4,308,079, teach the treatment of analuminum oxide surface of an aluminum substrate with a partialmonomolecular layer of an amino phosphonate compound such as nitrilotris(methylene) triphosphonic acid to retard hydration of the aluminum oxideto aluminum hydroxide to provide a more stable microporous surface whichis particularly suited to commercial adhesives. The formation of thehydrated oxide is said to interfere with the stability of a satisfactorybond between the adhesive and the oxide, while the phosphonate treatmentto form a partial monomolecular layer is said to be sufficient toinhibit the conversion of the oxide to hydroxide without interferingwith subsequent bonding of the adhesive to the oxide.

In the present invention, a novel food or beverage container orcontainer panel and a method of making the same are provided from coatedaluminum alloy sheet stock. The coating comprises a layer of aluminumoxide and/or hydroxide on the sheet and bonded thereto is a layer whichis comprised of the reaction product of phosphonic, phosphinic orphosphoric acid ester compounds such as monomeric or polymeric acids.

SUMMARY OF THE INVENTION

Disclosed is a food or beverage container or container panel comprisedof an aluminum alloy body having an integral bottom and wall. Anintermediate layer comprised of an aluminum oxide and/or aluminumhydroxide layer is bonded to the aluminum alloy body and afunctionalized layer of an organo phosphonate, organo phosphinate orphosphate ester is bonded to the oxide or hydroxide layer. A polymerlayer is bonded to the functionalized layer. The functionalized layer iscomprised of the reaction product of phosphonic or phosphinic acidand/or phosphoric acid ester, for example.

It is, therefore, an object of this invention to provide a novelaluminum food or beverage container or container panel.

It is a further object of this invention to provide a method of formingthe food or beverage container.

And, it is a further object of this invention to provide a novel lid orend for a food or beverage container.

These and other objects of the invention will be understood from thefollowing description and accompanying flow sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a container panel or lid in accordance with theinvention.

FIG. 2 is an easy open end or lid in accordance with the invention.

FIG. 3 is a cross section view of the lid of FIG. 1 in accordance withthe invention.

FIG. 4 illustrates a food or beverage container in accordance with theinvention.

FIG. 5 is an enlarged cross section view of the container wall inaccordance with the invention.

FIG. 6 is a top view of an easy open end or lid.

FIG. 7 illustrates the steps involved in forming a container or lid ofthe invention.

FIG. 8 shows the R groups extending away from a phosphonic acid treatedsurface.

FIG. 9 is a depth profile analysis by Secondary Mass Spectroscopy (SIMS)of the coatings of the invention.

FIG. 10 is a depth profile analysis by AES of a multilayer coating ofthe present invention formed by treatment with phosphonic acid.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, there is shown in FIG. 4 a beveragecontainer in accordance with the invention. The container body 6 has awall 10 and may have an integral aluminum bottom 8, as shown in FIG. 4.As shown in FIG. 5, the bottom 8 or side 10 of the container iscomprised of an aluminum wall 11 and a layer 12 of aluminum oxide and/oraluminum hydroxide. While the coating has been shown on both sides, itmay be applied to one side of the sheet which results in the inside ofthe container, as shown in FIG. 3. Bonded to the layer 12 of aluminumoxide or hydroxide is a layer 14 of a phosphorus-containing organicmaterial. A polymer layer 16 is bonded to layer 14 of thephosphorus-containing organic material. Preferably, the layer ofaluminum oxide or aluminum hydroxide, the phosphorus-containing organiclayer and polymer layer are applied to a flat sheet product which isthen formed to a container such as a food or beverage container orcontainer panel or lids therefor. Alternatively, the treatment may beapplied to the container panel or lid after forming. The layers have ahigh level of adherence to the aluminum body. This high level of bondstrength between the layers permits the drawing or redrawing of a flatblank into the food containers, for example. Further, the flat blankpermits the drawing and ironing to form a beverage container, asillustrated in FIG. 4. Even after drawing and ironing, the containerwall 10 retains the polymer firmly bonded thereto.

Likewise, a lid or end or container panel, such as shown in FIGS. 1 or2, is provided from blanks having layers of aluminum oxide or aluminumhydroxide, of phosphorus-containing organic material and of the polymer,as noted hereinbefore.

By the use of "container panel" herein is meant to include containerlids or ends, including easy open ends which have an integral rivet, topand scoreline and shallow trays such as food trays formed from aluminumfoil. Foil for such uses can have a thickness in the range of 0.003 to0.006 inch.

The lid or end design may be a conventional type 30 as shown in FIG. 1or it may be a conventional type with an opening therein for sealingwith an adhesive strip. Or, the lid design may be any of the easy opentype 50 (FIGS. 2 and 6) having an integral rivet 52, a tab 54 and scoreline 56 defining an opening for removing contents of the container.Further, the lid or end 30 or 50 may be made by any of the well knownstamping or forming processes to provide the type 30 design. Additionalforming steps to provide integral rivet 52 and score line 56 may beperformed without adversely affecting the layers or coatings.

Aluminum alloys for lids such as AA5182 are provided as an ingot orbillet by casting techniques currently employed in the art for castproducts with continuous casting being preferred. Prior to the principalworking operation, such alloy stock is preferably subjected tohomogenization. After homogenization, the ingot is hot worked or rolledto provide an intermediate gauge. Hot rolling is performed wherein thestarting temperature for rolling is in the range of 700° to 975° F. Whenthe use of the alloy is for beverage cans, such as end stock, the hotrolling is performed to provide an intermediate product having athickness of about 0.190 inch to 0.130 inch. Next, this material is coldrolled to provide a sheet ranging in thickness from about 0.008 to 0.015inch.

Aluminum alloys such as AA3004 or AA5042 for forming into cans bydrawing and redrawing for food containers, for example, or drawing andironing as for beverage containers, are first provided as an ingot andhomogenized. This is followed by hot rolling to a gauge of about 0.125inch. Typically, this is followed by anneal followed by hot rolling andthen cold rolling to a final gauge sheet product in the range of 0.011to 0.015 inch for forming into containers. Thereafter, typically blanksare cupped, wall ironed, bottom domed, necked and flanged.

For sheet used for lids or containers, it is preferred that coatings orlayers thereon of aluminum hydroxide or aluminum oxide, phosphonate,phosphinate and/or phosphate esters are thereto and polymer is bonded tothe phosphorus-containing compound. The preferred steps are shown inFIG. 7. In certain instances, applying the aluminum oxide layer andphosphonate, phosphinate or phosphate ester layer may occur in the samestep, as, for example, when the sheet is anodized in phosphonic orphosphinic acid or phosphoric acid ester including hydrogen phosphonicacid to apply these layers.

In accordance with one aspect of the invention, the aluminum sheet istreated to form an aluminum hydroxide coating thereon. Bonded to thehydroxide coating is a layer consisting essentially of a reactionproduct of a phosphorus-containing organic acid selected from the classconsisting of phosphonic acid, phosphinic acid, or a combination ofthese acids, referred to herein as a functionalized layer. Phosphoricacid esters may be used instead of phosphonic or phosphinic acids or incombination therewith. The acids or acid esters may be polymeric ormonomeric. The reaction product, e.g., phosphonate, phosphinate orphosphate ester, in accordance with the invention, exhibits a preferredorientation such that the phosphorus groups are bonded to the aluminumhydroxide on the surface while the R groups extend away from thatsurface, as illustrated in FIG. 8.

By polymer as used herein is meant to include a macromolecule formed bythe chemical union of five or more combining units which may be the sameor different monomers, dimers, trimers, etc.

Functionalized layer as used herein means a layer which can have achemical reactivity ranging from non-reactive to very reactive and whichcan be acid and base resistant, exhibit hydrophobicity orhydrophilicity, can be thermally stable at 250° C., for example, and behydration resistant.

By aluminum hydroxide as used herein is meant to include aluminumhydroxide and aluminum hydroxide in combination with aluminum oxides.

Phosphonic acid as used herein has the formula:

    R.sub.m [PO(OH).sub.2 ].sub.n

wherein R may be hydrogen or is one or more radicals having a total of1-30 carbons; m is the number of radicals in the molecule or compoundand is in the range of 1-10 for monomeric acids; n is the number ofphosphonic acid groups in the molecule or compound and is in the rangeof 1-10 for monomeric acids; and n and m can be higher for polymericphosphonic acids.

Phosphinic acid as used herein has the formula:

    R.sub.m R'.sub.o [PO(OH)].sub.n

wherein for monomeric acids, R may be hydrogen or is one or moreradicals having a total of 1-30 carbons; m is the number of R radicalsin the molecule or compound and is in the range of 1-10; R' may behydrogen or may be comprised of 1-30 carbon-containing radicals; o isthe number of R' radicals and is in the range of 1-10; n is the numberof phosphinic acid groups in the molecule or compound and is in therange of 1-10, and for polymeric acids, the numbers for m, n and o canbe considerably higher.

Phosphonic or phosphinic acid as used herein may include monomeric andpolymeric phosphonic or phosphinic acids and such compounds which canform acid radicals in solution.

Phosphoric acid esters as used herein is meant to include mono-, di-,tri- to dodeca- phosphoric acid radicals and both monomeric andpolymeric phosphoric acid esters, and salts thereof are useful in theinvention. Phosphoric acid esters may be defined by the formula:(RO)_(m) [PO(OH)₂ ]_(n) or (RO)_(m) (R'O)_(k) [PO(OH)]_(n) or (RO)_(m)(R'O)_(k) (R"O)_(q) [PO]_(n) wherein for monomeric acids R is one ormore radicals having a total of 1-30 carbons; R' and R" is one or moreradicals having a total of 1-30 carbons; m, k or q is the number ofradicals RO, R'O or R"O, respectively, in the molecule or compound andis in the range of 1-12; and n is the number of phosphoric acid groupsin the molecule or compound and is in the range of 1-12. For polymericphosphoric acid ester, these numbers for m, n, k and q will beconsiderably higher. It will be appreciated that for polymericphosphonic or phosphinic acids or phosphoric acid esters m, k, q, o, ncan be as high as 250,000, for example.

Phosphoric acid ester salt as used herein has the formula (RO)PO(OX)₂ or(RO)PO(OH)(OX) or (RO)(R'O)PO(OX) wherein R or R' is one or moreradicals having a total of 1-30 carbons and x is selected from ammonia,alkali, alkaline earth and transition metals.

In the invention, the aluminum sheet product is subjected to ahydroxylating treatment. That is, the product is treated with water,water-containing vapor, e.g., steam, or an aqueous solution having a pHin the range of 2 to 12, preferably a pH in the range of 7 to 10. Thistreatment forms a layer of aluminum hydroxide on the surface of thealuminum sheet product. Aluminum hydroxide as used herein may have theformula AlOOH or Al(OH)₃ or nonstoichiometric versions thereof and caninclude partially hydroxylated oxide layers, depending somewhat on thetemperature of the solution. For example, while the treatmenttemperature of the solution can range from room temperature to about200° C., temperatures of 70° to 200° C. tend to favor formation ofAlOOH, and room temperature of about 70° C. tend to favor formation ofAl(OH)₃. The layer of aluminum hydroxide is less than 5000 Å andpreferably less than 1000 Å with typical thicknesses being in the rangeof 50 to 850 Å.

While treatment with water vapor at temperatures above 100° C. providesvery fast hydroxylation, the need for pressure vessels makes thisapproach less desirable. Sufficient hydroxylation within seconds canalso be achieved by the use of mildly alkaline solutions of pH of 8-10at temperatures near boiling.

Aqueous solutions suitable for use in providing a hydroxylated surfacecan be water combined with a basic material which may be organic orinorganic. Suitable basic materials which may be used include organicamines, e.g., triethanol amine, propyl amine, triethyl amine, alkalimetal hydroxides, alkaline earth metal hydroxides, ammonium hydroxideand alkali metal carbonates or bicarbonates. It will be appreciated thatthe hydrolysis of acid salts also will result in the formation of thehydroxylated surface, e.g., treatment of an aluminum surface with waterafter it has been treated or immersed in an inorganic oxy acid, e.g., H₂SO₄ acid. To prepare the solution, a sufficient amount of the basic oracidic material is added to water to adjust the pH to the desired level.

Time of treatment can be as short as one second. Treatment times canrange from 1 to 100 seconds or longer, e.g., 5 to 10 minutes, withpreferred times being 1 to 30 seconds, and typical times being in therange of 5 to 10 seconds.

After hydroxylating, the aluminum is treated in a solution of phosphonicacid, phosphinic acid or phosphoric acid ester, either monomeric orpolymeric, a combination of such acids or phosphoric acid esters.

The solution or liquid used in the treatment of the aluminum surfacepreferably comprises a solvent, e.g., water, alcohol or organicsolvents, with a range of concentration of from about 0.001 molar to asaturated solution, preferably about 0.1 to about 2 molar, of a 1-30carbon, preferably 2-12 carbon, phosphonic acid; one or more 1-30carbon, preferably 2-12 carbon, phosphinic acid; analogous phosphoricacid esters, 1-30 carbon phosphoric acid esters; or a mixture of thesame. The acids may be monomeric or polymeric. The solution may besprayed or immersed. The metal is treated by contacting the surface withthe solution, which contacting can include the preferred methods ofspraying or immersing.

Examples of groups which may comprise R, R' and/or R" include long andshort chain aliphatic hydrocarbons, aromatic hydrocarbons, carboxylicacids, aldehydes, ketones, amines, amides, thioamides, imides, lactams,anilines, pyridines, piperidines, carbohydrates, esters, lactones,ethers, alkenes, alkynes, alcohols, nitriles, oximes, allyls, vinyl,ureas, thioureas, silanes and combinations of these groups.

Representative of the polymeric phosphonic acids are as follows:polyvinyl phosphonic acid, poly(vinylbenzyl)phosphonic acid,poly(2-propene)phosphonic acid, phosphonomethyl ethers of cellulose,phosphonomethyl ethers of polyvinyl alcohol, poly 2-butene phosphonicacid, poly 3-butene phosphonic acid, phosphonomethyl ethers of starch,polystyrene phosphonic acid, polybutadiene phosphonic acid andpolyethylene imine methyl phosphonate.

Representative of the monomeric phosphonic/phosphinic acids are asfollows: aminobenzylphosphonic acid, phosphomycin, 3-amino propylphosphonic acid, vinyl phosphonic acid, allyl phosphonic acid,4-methoxyphenyl phosphonic acid, aminophenylphosphonic acid,aminophosphonobutyric acid, aminopropylphosphonic acid,benzhydrylphosphonic acid, benzylphosphonic acid, butylphosphonic acid,carboxyethylphosphonic acid, diphenylphosphinic acid, dodecylphosphonicacid, ethylidenediphosphonic acid, ethylphosphonic acid,heptadecylphosphonic acid, hydrogen phosphonic acid,methylbenzylphosphonic acid, methylphosphonic acid,naphthylmethylphosphonic acid, octadecylphosphonic acid, octylphosphonicacid, pentylphosphonic acid, phenylphosphinic acid, phenylphosphonicacid, phosphonopropionic acid, phthalide-3-phosphonic acid and styrenephosphonic acid.

Representative of the polymeric phosphoric acid esters are polyvinylphosphoric acid ester, dodecylpolyoxy ethylene phosphoric acid ester,phosphate-containing polymers, phosphorylated starch, complex sugars andcellulose, Fyrol 99, Fyrol 51, Tex-Wet 1131, phosphate esters ofpolyvinyl alcohols, polyacrylamides, homopolymers and random polymers ofamino acids, polyethylene glycol, polynucleotides, polyoxyethylene andpolystyrene.

Representative of monomeric phosphate esters are tris(dibromopropyl)phosphate, Thermolin 101, Phosgard 1227, Tricresyl phosphate, polyarylphosphate, octyl phosphate, dioctyl phosphate, trioctyl phosphate,glycerol 1-phosphate, phosphonenolpyruvate, glucose 1-phosphate,pantothenic acid, phytic acid, Ethfac®, Klearfac®, acetyl phosphate,adenosine 2',5'-diphosphate, 3'-Adenylic acid, adenylosuccinic acid,Agrocin 84, 2-(phosphonooxy)benzoic acid, picosforic acid,mono(2-cyanophenyl)phosphate, Meonomycin and vinyl phosphoric acidester.

The phosphonic/phosphinic acid or phosphoric acid ester molecules suchas listed above may also include inorganic groups substituted thereonsuch as phosphates, and the like, or groups such as phosphonates,sulfonates, or carbonates. While it is preferred that the free end ofthe organic group extends away from the aluminum oxide/hydroxidesurface, it is within the scope of the present invention to provide, onthe free end of the molecule, functional groups. The term functionalgroup may be defined as the group on the molecule which enables thephosphonic/phosphinic acid molecule bonded to the aluminum oxide surfaceto react with, attract, couple to, or bond with, etc., other atoms, ionsand/or molecules.

It should be noted that the free end of the phosphonic/phosphinic acidor phosphoric acid ester molecule may be further reacted after formationof the layer on the aluminum surface to provide the desiredfunctionalization of the molecule discussed above if suchfunctionalization of the phosphonic/phosphinic acid or phosphoric acidester prior to treatment of the aluminum surface would interfere withsuch treatment or with the bond formed between the aluminum hydroxidelayer formed during the treatment and the acid group of thephosphonic/phosphinic acid molecule. In this manner, chemical bonding ofthe phosphorus-containing acid group of the phosphonic/phosphinic acidor phosphoric acid ester molecule to the aluminum hydroxide surface canbe assured.

To form the coating thereon, the aluminum surface should preferably, butnot necessarily, first be cleaned to remove any contaminants or excesssurface oxides using, for example, a mineral acid such as nitric,phosphoric, or sulfuric acid, or a base such as NaOH, after which thesurface is rinsed with water.

After the aluminum surface has been cleaned, it may be immersed in thehydroxylating liquid maintained at a temperature in the range of fromjust above freezing to just below boiling, preferably from about 50° C.to about 100° C.

Subsequent treatment with phosphonic or phosphinic acid or phosphoricacid ester provides a functionalized layer which is usually less than1000 Å thick and usually less than 200 Å thick and greater than 5 Å,with a typical thickness being in the range of about 30 to 100 Å.

The result is an aluminum surface having a coating formed thereon andbonded to the aluminum surface comprising a first hydroxylated layer anda layer of phosphonic and/or phosphinic acid or phosphoric acid esterbonded to the aluminum hydroxide layer.

With respect to the bonding of the phosphonic and/or phosphinic acidmolecule or phosphoric acid ester to the aluminum hydroxide surface,while we do not wish to be bound by any particular theory of bonding, alayer of phosphonic/phosphinic acid is formed or bonded uniformly to thehydroxyl layer.

The reaction is believed to be as follows: ##STR1##

Examination of the layers of the subject invention by ElectronSpectroscopy for Chemical Analysis (ESCA) shows a high ratio of aluminumto phosphorus. That is, aluminum can be about 6 to 30 times that ofphosphorus. This shows that the organic acids are not incorporated intothe oxide barrier layer but are bonded on the surface of the layer. Thatis, depth profiles by Secondary Ion Mass Spectroscopy (SIMS) of theduplex layer or coating formed in accordance with the subject inventionusing phenyl phosphonic acid (FIG. 9) shows the amount of carbon andphosphorus dropping very quickly in the first minutes of sputteretching. This shows that these elements (carbon and phosphorus) are onthe surface.

Another method of applying the functionalized layer includes anodizingthe sheet product. That is, the sheet product may be immersed in thetreatment liquid, e.g., liquid containing phosphonic or phosphinic acidor phosphoric acid esters or combinations thereof, in an anodizingapparatus in which the treatment liquid is maintained at a temperaturewhich may range from just above freezing to just below boiling,preferably from about 5° C. to about 60° C. The temperature is selectedsuch that the solubility of phosphonate, phosphinate or phosphate estercomplexes of aluminum are low. It will be appreciated that the liquid orelectrolyte may also contain inorganic acids such as sulfuric,phosphoric, chromic and boric or organic acids such as oxalic, maleic,tartaric, etc.

The aluminum surface is electrically connected to the positive terminalof a power supply. A counter electrode is then connected to the negativeelectrode of the power supply.

The cleaned aluminum surface is then anodized at a voltage in the rangeof 1 to 400 volts, preferably from about 20 to 90 volts. Voltage usedmay be of several types, e.g., square wave, asymmetrical square wave,asymmetrical sine wave or saw tooth asymmetrical.

The result is an aluminum surface having a coating formed thereon andbonded to the aluminum surface comprising a first layer of anodicallyformed aluminum oxide and a layer of phosphonic or phosphinic acid orphosphoric acid esters, preferably monomeric phosphonic/phosphinic acidbonded to the aluminum oxide layer.

The oxide layer may be the porous or the non-porous type and isfunctionalized as in FIG. 8. FIG. 8 represents the outer surface of theduplex coating and, also, the inner pore walls of porous type duplexcoatings.

The thickness of the resulting functionalized oxide layer is in therange of 3-5000 Å and preferably 5 to 500 Å.

Examination of the layers of the subject invention by ElectronSpectroscopy for Chemical Analysis (ESCA) shows a high ratio of aluminumto phosphorus. That is, aluminum can be about 6 to 30 times that ofphosphorus. For example, the ratio of aluminum to phosphorus when monovinyl phosphonic acid, allylphosphonic acid, and phenyl phosphonic acidwere used as electrolytes were 24.1/3.0, 27.8/1.6, and 33.1/1.4,respectively. The phosphorus to aluminum ratio can range from 0.001 to0.5, preferably, 0.02 to 0.2. See Table 1 below.

                  TABLE 1                                                         ______________________________________                                        Atomic Concentrations Determined by ESCA (%)                                  Sample    Al        O      P      C    Al/P                                   ______________________________________                                        1M VPA.sup.(1)                                                                          24.1      27.1   3.0    45.8 8.00                                   1M APA.sup.(2)                                                                          27.8      30.8   1.6    39.8 17.2                                   1M PPA.sup.(3)                                                                          25.6      43.8   0.9    26.4 28.4                                   ______________________________________                                         .sup.(1) Mono vinyl phosphonic acid                                           .sup.(1) Allylphosphonic acid                                                 .sup.(1) Phenyl phosphonic acid                                          

Sputtering depth profiles by Auger Electron Spectroscopy (AES) of acoating formed in accordance with the subject invention using phenylphosphonic acid (FIG. 10) shows the amount of carbon and phosphorusdecreasing very quickly in the first minute of sputtering (50 Å/min).This shows that these elements (carbon and phosphorus) are on thesurface and constitute the functionalized layer. By comparison, oxygenconcentration starts and is maintained at a high level for about thefirst 15 minutes before starting to drop off when the aluminum signal ofthe base metal starts to increase, showing the anodic oxide layer has arelatively constant composition of Al₂ O₃.

Polymer formulations which may be used are epoxies, phenolic orpolyester modified epoxies, poly(vinyl chloride), carboxylated, epoxy ormelamin modified, PVC-vinyl acetate copolymers, ethylene vinyl acetate,polyesters, acrylic resins, polyethylene, other polyolefins or mixtures,polyamides, polystyrene and polyurethanes.

Thus, it will be seen that metal surfaces can be modified by the use ofthe functionalized layer to achieve higher performance in all types ofcoating and laminating.

Sheet stock produced in accordance with the present invention issuitable for use in can bodies or as end stock for easy open endsparticularly when coated with a polymeric material. Such polymericmaterials can be applied to the duplex coatings of the invention withresulting superior bond strengths, particularly if such polymericcoatings are bonded using reactive groups on the functionalized layer.The polymer coatings can be applied, for example, by spraying, dipping,roll coating, laminating, powder coating and then formed intocontainers.

Coatings in accordance with the invention were prepared as set forth inthe following Examples.

EXAMPLE 1

AA5042 alloy sheet, 0.010 inch thick, was cleaned by immersion in sodiumcarbonate solution, rinsed with water and then treated for 10 seconds inboiling water adjusted to pH 9 with triethanolamine. After rinsing withwater, the sheet was immersed for another 10 seconds in a 1 molarsolution of vinyl-phosphonic acid at room temperature. After rinsing anddrying, the sheet was examined by SIMS depth profiling analysis andfound to have a carbon/phosphorus layer over an aluminum oxide/hydroxidelayer. Next, the sheet was coated with a solvent-based, epoxy-modifiedpolyvinylchloride coating. After curing of the polymer coating, thesheet was bent 180°, and the bent area was flattened by dropping aweight on it (impact bend test). The coating was examined after thistest and given an adhesion rating of 5, i.e., the highest on a scale of1-5.

EXAMPLE 2

Samples of AA3003, 0.005 inch thick, foil were treated as in Example 1.One set of samples was coated with a polyvinyl chloride coating, asecond one with an epoxy coating. After curing, the dry coatings weretested with the tape adhesion test. No failure was observed. The sampleswere then immersed for 45 minutes in boiling water and tested by thetape adhesion test. Again, no failure was observed.

EXAMPLE 3

Samples having the treatments and coatings as in Example 3 weresubjected to even more severe test procedures. That is, samples weresubjected to a solution of lactic acid in water for 30 minutes at 175°C. (350° F.) or to a mixture of lard and water under the sametime/temperature conditions. Tape tests after these treatments showed noloss of adhesion and visual inspection did not reveal blistering of thecoating.

EXAMPLE 4

AA5042 was used for test specimens which were cleaned in an alkalinesolution and anodized at 10 or 40 volts for 10 seconds in 9 wt. % or 18wt. % vinyl phosphonic acid. In addition, these specimens were thencoated with a polyvinylchloride polymer and fabricated into cans. Theperformance was equivalent to that of metal receiving a conventionalchromate conversion coating in terms of coating adhesion and resistanceto corrosion under test conditions simulating processing and storage offilled containers. The vinylphosphonic acid treated cans had an averagesidewall adhesion tape test result of 95% adhesion, whereas theconventional chromate conversion coated cans had an average 91% sidewalladhesion with the tape test.

EXAMPLE 5

AA5182 was used for test specimens which were cleaned in alkalinesolution and anodized at 10 or 40 volts for 10 seconds in 9 wt. % or 18wt. % vinyl phosphonic acid. In addition, these specimens were thencoated with an epoxy melamine polymer and fabricated into can end stock.The performance was equivalent to that of metal receiving a conventionalchromate conversion coating in terms of adhesion and resistance tocorrosion under test conditions simulating processing storage of filledcontainers. All samples passed adhesion and corrosion tests aftertreatment in 160° F. water and 160° F. beer.

EXAMPLE 6

This example was the same as Example 4 except that the cleaned sheet wasanodized at 10 volts for 10 seconds in a solution containing 15 wt. %vinylphosphonic acid and 7.5 wt. % phosphoric acid. After forming intocans, the anodized sheet had an average sidewall adhesion tape testresult of 99% adhesion, compared to 91% adhesion for conventionalchromate conversion coated sheet.

EXAMPLE 7

This example was the same as Example 5 except the cleaned sheet wasanodized at 10 volts for 10 seconds in a solution containing 15 wt. %vinylphosphonic acid and 7.5 wt. % phosphoric acid. After forming intoeasy open ends, the ends passed all adhesion, corrosion and featheringtests. Furthermore, the anodized ends had an average enamel rating of0.06 mA compared to 0.12 mA for conventional chromate conversion coatedsheet. Feathering is a measure of coating adhesion after opening theends. Enamel rating is an electrical measure of coating continuity.

EXAMPLE 8

Specimens of AA3003 alloy, anodized at 20 volts in 20 wt. % hydrogenphosphonic acid at 23° C. for 10 seconds, were coated with polyvinylchloride or polyvinyl acetate, to provide a high level of adhesion.There was no loss of adhesion when treated in lactic acid or lard/watersolutions for 30 minutes at 350° F.

EXAMPLE 9

AA3003 foil (0.005"), both -O and -H19 tempers, was boiled for 10seconds in water containing triethanolamine at pH 9. The foil was rinsedwith deionized water and then dipped in 18 wt. % vinylphosphonic acidsolution for 10 seconds. The foil was rinsed with deionized water, driedand coated with polyvinyl chloride or polyvinyl acetate to provide ahigh level of adhesion. There was no loss of coating adhesion aftertreatments for 30 minutes at 350° F. in: 1) lactic acid/salt solution;2) lard/water; 3) ketchup/vinegar/vegetable oil; 4) lemon juice; 5)orange oil; or 6) hot sauce.

EXAMPLE 10

This example was the same as Example 9 except that the boiled foil wasdipped in 5% hydrogen phosphonic acid for 10 seconds. There was no lossof adhesion after treatment in the various process mixtures.

EXAMPLE 11

This example was the same as Example 9 except the boiled foil was dippedin 1 wt. % phytic acid. There was no loss of adhesion after treatment inthe various process mixtures.

EXAMPLE 12

This example was the same as Example 9 except that the foil was firstboiled in 0.1 m tribasic sodium phosphate solution for 10 seconds. Thefoil was rinsed, then dipped in 18% vinylphosphonic acid for 10 secondsthen coated as in Example 8. There was no loss of coating adhesion aftertreatment in the various process mixtures.

Thus, the invention provides a process for forming a protective coatingon a metal surface comprising a first layer of a metal hydroxide and alayer of phosphonic/phosphinic acid phosphoric acid ester chemicallybonded to the metal oxide or hydroxide layer.

Having thus described the invention, what is claimed is:
 1. A food orbeverage container or container panel comprised of:(a) an aluminum alloybody having an integral bottom and wall; (b) an intermediate layercomprised of an aluminum oxide or aluminum hydroxide layer bonded tosaid aluminum alloy body and a functionalized layer bonded to saidaluminum oxide or aluminum hydroxide layer, said functionalized layercomprising a reaction product of aluminum oxide or aluminum hydroxidewith(i) a phosphinic acid having the formula R_(m) R'_(o) [PO(OH)]_(n)wherein R may be hydrogen or is one or more radicals having a total of1-30 carbons; m is the number of R radicals; R' may e hydrogen or may becomprised of 1-30 carbon-containing radicals; o is the number of R'radicals; and n is the number of phosphinic acid groups; or (ii) aphosphate ester having the formula (RO)_(m) [PO(OH)₂ ]_(n) or (RO)_(m)(R'O)_(k) [PO(OH)]_(n) or (RO)_(m) (R'O)_(k) (R"O)_(q) [PO]_(n) whereinfor monomeric acids, R is one or more radicals having a total of 1-30carbons; R' and R" are one or more radicals having a total of 1-30carbons; m, k and q are the number of radicals RO, R'O and R"O,respectively, in the ester; and n is the number of phosphoric acidgroups in the ester; and (c) a polymer layer bonded to saidfunctionalized layer.
 2. The container in accordance with claim 1wherein the intermediate layer has a thickness of less than 6000 Å. 3.The container in accordance with claim 1 wherein the intermediate layerhas a thickness of less than 1500 Å.
 4. The container in accordance withclaim 1 wherein the intermediate layer has a thickness of 50 to 1500 Å.5. The container in accordance with claim 1 wherein the intermediatelayer has a thickness of 100 to 500 Å.
 6. The container in accordancewith claim 1 wherein the oxide or hydroxide layer has a thickness ofless than 5000 Å.
 7. The container in accordance with claim 1 whereinthe oxide or hydroxide layer has a thickness of less than 1000 Å.
 8. Thecontainer in accordance with claim 1 wherein the aluminum hydroxidelayer has a thickness in the range of 100 to 850 Å.
 9. The container inaccordance with claim 1 wherein the functionalized layer has a thicknessof less than 200 Å.
 10. The container in accordance with claim 1 whereinthe functionalized layer has a thickness of less than 100 Å.
 11. Thecontainer in accordance with claim 1 wherein the functionalized layerhas a thickness in the range of 5 to 50 Å.
 12. The container inaccordance with claim 1 wherein the aluminum wall has a thickness in therange of 0.02 to 0.003 inch.
 13. The container in accordance with claim1 wherein the hydroxide layer results from a treatment in an aqueoussolution containing triethanol amine at a pH in the range of 2 to 12.14. The container in accordance with claim 1 wherein the functionalizedlayer is comprised of the reaction product of phosphinic acid andaluminum hydroxide and the phosphinic acid has the formula R_(m) R'_(o)[PO(OH)]_(n) wherein R may be hydrogen or is one or more radicals havinga total of 1-30 carbons; m is the number of R radicals; R' may behydrogen or may be comprised of 1-30 carbon-containing radicals; o isthe number of R' radicals; and n is the number of phosphinic acidgroups.
 15. The container in accordance with claim 1 wherein thefunctionalized layer is comprised of a phosphate ester which is thereaction product of a phosphoric acid ester with aluminum hydroxide andhas the formula (RO)_(m) [PO(OH)₂ ]_(n) or (RO)_(m) (R'O)_(k)[PO(OH)]_(n) and (RO)_(m) (R'O)_(k) (R"O)_(q) [PO]_(n) wherein formonomeric acids R is one or more radicals having a total of 1-30carbons; R' and R" is one or more radicals having a total of 1-30carbons; m, k or q is the number of radicals RO, R'O or R"O,respectively, in the molecule or compound; and n is the number ofphosphoric acid groups in the molecule or compound.
 16. A food orbeverage container panel or container body comprising:(a) an aluminumalloy lid or an aluminum alloy body having an integral bottom and sidewall, said lid or body having a thickness in the range of 0.003 to 0.02inch; (b) an intermediate layer bonded to said lid or body, saidintermediate layer comprising an aluminum hydroxide layer attached tosaid lid or body and having a thickness of less than 1000 Å; (c) afunctionalized layer chemically bonded to the aluminum hydroxide layerand comprising a reaction product of aluminum hydroxide with aphosphonic acid having the formula R_(m) [PO(OH)₂ ]_(n) wherein the Rmay be hydrogen or is one or more radicals having a total of 1-30carbons; m is the number of radicals; and n is the number of phosphonicacid groups, said functionalized layer having a thickness of less than200 Å; and (d) a polymer layer bonded to said functionalized layer. 17.The container panel or container of claim 16 wherein the lid or body isa lid.
 18. The container panel or container of claim 16 wherein the lidor body is a body.
 19. The container panel or container of claim 16wherein the lid or body comprises a foil having a thickness in the rangeof 0.003 to 0.006 inch.
 20. The container panel or container of claim 16wherein the lid or body has a thickness of about 0.008 to 0.015 inch.21. The container panel or container of claim 16 wherein theintermediate layer has a thickness in the range of 50 to 850 Å.
 22. Thecontainer panel or container of claim 16 wherein the functionalizedlayer comprises a reaction product of aluminum hydroxide and vinylphosphonic acid.
 23. The container panel or container of claim 16wherein the functionalized layer has a thickness of less than 100 Å. 24.The container panel or container of claim 16 wherein the functionalizedlayer has a thickness in the range of 5 to 50 Å.
 25. The container panelor container of claim 16 wherein said polymer layer comprises a polymerselected from the group consisting of polyvinyl chloride, polyvinylacetate and an epoxy.
 26. The container panel or container of claim 16wherein said polymer layer comprises polyvinyl chloride.
 27. A food orbeverage container panel or container body comprising:(a) an aluminumalloy body having an integral bottom and side wall or an aluminum alloylid; (b) an intermediate layer bonded to said body or lid, saidintermediate layer comprising an anodized aluminum oxide layer attachedto said body or lid and having a thickness of 100 to 500 Å; (c) afunctionalized layer chemically bonded to the aluminum oxide layer andcomprising ar reaction product of aluminum oxide with a phosphonic acidhaving the formula R_(m) [PO(OH)₂ ]_(n) wherein R may be hydrogen or isone or more radicals having a total of 1-30 carbons; m is the number ofradicals, and n is the number of phosphonic acid groups, saidfunctionalized layer having a thickness of less than 200 Å; and (d) apolymer layer bonded to said functionalized layer.
 28. The container inaccordance with claim 27 wherein said body or lid has a thickness of0.003 to 0.02 inch.
 29. The container in accordance with claim 27wherein the functionalized layer comprises a reaction product ofaluminum oxide and vinyl phosphonic acid.
 30. The container inaccordance with claim 27 wherein the functionalized layer has athickness in the range of 5 to 50 Å.
 31. The container in accordancewith claim 27 wherein said polymer layer comprises a polymer selectedfrom the group consisting of polyvinyl chloride, polyvinyl acetate andan epoxy.